Cynnamin..., you know english it´s not my language... but I´ll try to explain some things...
I´m biochemist, and I know molecular bases of Calcium deposits, absortion, vitamine D metabolism and production... etc, etc, etc...
First of all, calcium is an element present in all our food... specially meat, because it´s necessary for muscular contraction. Extra calcium added in milk is, most of the time, excreted ( pissed ). Calcium absortion it´s not simply aided by vitamine D, this vitamine is required to do that, and it´s the amount of vitamine the limitant factor in exogen calcium absortion, not the calcium you eat or drink. So, you can drink cow milk, or soy milk, or holy milk, or other potion, and you´ll win nothing, since the amount of calcium you are going to absorve it´s limited day after day. Other thing: calcium is a massive element, suffer a lack of calcium it´s impossible, so, it´s a waste of time add an extra source of it.
Sun... it´s needed to properly form Vitamine D, but this mollecule, with the rest of vitamins, it´s only an enzimatic cofactor required in residual amount. That is: the sun in your face when you are going to buy bread is more than enough.
More things... men and osteoporosis. Normal osteoporosis in women is produced by a lack of calcitonine ( activator of osteoblasts and inhibitor or osteoclasts ) in menopause. In that moment bone starts to loss mass, when this hormone reduces its presence. But, in men, this a genetical factor, and only genetical. That means: if a man is going to suffer osteoporosis he will became ill ALWAYS, drinking 500 litres of soy milk or not. So, a man worried by osteoporosis is a non sense thing, because he can do nothing to avoid it. Ah ! and the same thing happens with women suffering osteoporosis before menopause.
P.D: Now, you are going to say that vitamine D is added in soy milk. It has no effect, because I said vitamine is only a enzimatic COFACTOR ( an enzime´s helper ), and is the ENZIME, and not the vitamine, the true limitator in the process of calcium absortion.